[asterisk-dev] Realtime caching or something else? (SIP retransmit#1)

[Watkins, Bradley]

I certainly am most interested in static realtime, although it would be
nice to be able to mark a user/peer/whatever to always be in memory (in
the case where you don't have registrations for that entry).  Also, I
think manager and CLI commands are requisite for getting new entries.

Regards,
- Brad 

> -----Original Message-----
> From: asterisk-dev-bounces at lists.digium.com 
> [mailto:asterisk-dev-bounces at lists.digium.com] On Behalf Of 
> Olle E Johansson
> Sent: Tuesday, October 31, 2006 7:59 AM
> To: Asterisk Mailing List Developers
> Subject: [asterisk-dev] Realtime caching or something else? 
> (SIP retransmit#1)
> 
> Friends,
> 
> The realtime caching in chan_sip is beginning to annoy me. I 
> think there's a great confusion here and we need to create a roadmap.
> 
> For me, "caching" is controlled by the software. In order to 
> avoid extra access to storage, we keep stuff in memory so 
> they can be retrieved faster when needed. The software is in 
> control and can release memory allocated by objects at any time.
> 
> In chan_SIP, developers are trying to extend "caching" to "static".  
> Let me explain.
> 
> We have static and realtime devices.
> 
> * Static are loaded in memory at startup and stays in memory, 
> regardless of registration status.
> 
> * Realtime are loaded in memory when needed and then released 
> as quick as possible.
> 
> Realtime objects are not meant to stay in memory and provide 
> services. Asterisk should be able to delete them at any time, 
> without loosing functionality.
> 
> The caching was implemented for performance. As a side 
> effect, we could provide some extra functionality like NAT 
> traversal support (qualify) and MWI notification until the 
> object is deleted from memory.  This is where the problem 
> starts. From reading the bug reports, users need something else.
> 
> What users seem to want is a way to load static objects, that 
> stay in memory, from realtime storage. Delete them when we 
> have no registration (expiry or
> unregister) and load them when they
> register again.
> 
> This is *not* caching. This is a new mechanism that we do not 
> support today, but users seem to think that we support - thus 
> filing a lot of bug reports.
> 
> I don't want to continue fixing a broken implementation. My 
> suggestion:
> 
> * Implement real caching: A configuration option that says 
> how many devices we should keep in memory (a max level) and a 
> way to determine which ones to expire when we hit this level. 
> Do *not* provide NAT keepalives or MWI for these.
> Maybe we need manager/CLI commands for deleting cached 
> objects that have changed in the database.
> 
> * Implement static realtime: When a device registers, load it 
> in memory from realtime storage and keep it in memory. 
> Provide services like NAT keepalives and MWI during registration.
> Only delete these from memory when they unregister or 
> registration expires.
> 
> * We could additionally implement manager commands (and CLI) 
> for forcing a load
>    into memory from static storage. So if you configure for 
> static and add a device during
>    runtime, there's no need for full reload, just tell 
> asterisk that there's a new device
>    that needs to be loaded into memory.
> 
> I think we need to discuss this and decide on what we want to do.  
> Today, what we
> actually deliver and what users believe we deliver does not 
> match, which results in extra bug reports.
> 
> When we approach IM outside of a call, it's very important 
> that we have a cleaner implementation than we have today.
> 
> /O
> 
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